Why are some of my Google Vision API DOCUMENT_TEXT_DETECTION results' normalizedVertices greater than 1? - rest

Question

I have implemented an OCR invoice solution using Google Vision API DOCUMENT_TEXT_DETECTION service. The software has been in production for a couple months. 99% of the time, the results are pretty accurate. But every once in a while, I get some results containing normalizedVertices with points greater than 1. According to the docs, a normalized vertex should be between 0 and 1. Anyone know why this happens? And how these should be interpreted?
Only thing I have noticed (in conjunction with this issue) is that often the documents producing these results may be rotated. But I don't see why rotation would cause the normalization to be off.
Here's a sample file
{
"fullTextAnnotation": {
"pages": [
{
"property": {
"detectedLanguages": [
{
"languageCode": "en",
"confidence": 0.84
},
{
"languageCode": "da",
"confidence": 0.01
}
]
},
"width": 612,
"height": 792,
"blocks": [
{
"boundingBox": {
"normalizedVertices": [
{
"x": 1.2254902,
"y": 0.79545456
},
{
"x": 1.2254902,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.79545456
}
]
},
"paragraphs": [
{
"boundingBox": {
"normalizedVertices": [
{
"x": 1.2254902,
"y": 0.79545456
},
{
"x": 1.2254902,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.79545456
}
]
},
"words": [
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"boundingBox": {
"normalizedVertices": [
{
"x": 1.2254902,
"y": 0.79545456
},
{
"x": 1.2254902,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.9166667
},
{
"x": 1.1960784,
"y": 0.79545456
}
]
},
"symbols": [
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "I",
"confidence": 0.99
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "N",
"confidence": 1
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "V",
"confidence": 0.99
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "O",
"confidence": 0.99
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "I",
"confidence": 0.99
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
]
},
"text": "C",
"confidence": 0.99
},
{
"property": {
"detectedLanguages": [
{
"languageCode": "en"
}
],
"detectedBreak": {
"type": "LINE_BREAK"
}
},
"text": "E",
"confidence": 1
}
],
"confidence": 0.99
}
],
"confidence": 0.99
}
],
"blockType": "TEXT",
"confidence": 0.99
},...